Huh? Bet or no?

[Jimbobobb]

Party Poker 0.50/1 Hold'em (7 handed)

Preflop: Hero is UTG with 9/images/graemlins/diamond.gif, 9/images/graemlins/spade.gif.
Hero calls, MP1 calls, MP2 folds, CO calls, Button folds, <font color="CC3333">SB raises</font>, BB folds, Hero calls, MP1 calls, CO calls.

Flop: (9 SB) 6/images/graemlins/club.gif, 3/images/graemlins/club.gif, 6/images/graemlins/diamond.gif <font color="blue">(4 players)</font>
SB checks, <font color="CC3333">Hero bets</font>, MP1 calls, CO calls, SB calls.

Turn: (6.50 BB) 7/images/graemlins/heart.gif <font color="blue">(4 players)</font>
SB checks, <font color="CC3333">Hero bets</font>, MP1 calls, CO calls, <font color="CC3333">SB raises</font>, Hero calls, MP1 calls, CO calls.

River: (14.50 BB) 3/images/graemlins/diamond.gif <font color="blue">(4 players)</font>
SB checks, Hero........

wha? ummm alright..... I don't know about betting this river. If I get c/raised I seriously might just throw up. There are also 2 other people in the hand, and maybe one has a 3 or a 6.....I think betting this river is ridiculous, and I don't know how to respond to a bet.....but I dunno. I was confused with this hand. Any and all comments welcome.

edit: I honestly don't have any real reads on these guys....SB is:

40% vpip
15% pfr

over 108 hands

[Bez]

Check seems to be correct here with other players in but I would call a single bet.

[Brain]

I check/call the river and probably fold if it happens to be 2 back to me.

I'd really like to put SB on overcards, but I can't do it with any confidence.